A downhole tool for performing an acid stimulation operation includes a chamber and at least one acid resistant container to store a stimulation fluid comprising a stimulation acid. The at least one acid resistant container can be placed in the chamber prior to conveying the downhole tool in a borehole. The downhole tool can include a fluid injector fluidly coupled to an output of the chamber. After the downhole tool is positioned at a location in the borehole where the stimulation fluid is to be injected into a subsurface formation surrounding the borehole, the at least one acid-container can be opened such that the stimulation fluid can flow from the output of the chamber to the fluid injector. The fluid injector can inject the stimulation fluid into the subsurface formation.